1. Field of the Invention
The present invention relates to a numerical controller which controls a plurality of axes, including an axis to be a follow-up target axis in synchronization and an axis to be a follow-up axis in synchronization, and a control method for performing synchronous control using the numerical controller so that the follow-up axis follows up the follow-up target axis.
2. Description of the Related Art
In an application for moving a tool in stopping status and processing a work which is moving by a conveyer driven by an axis, for example, synchronous control is performed by synchronizing a drive axis (follow-up axis) of moving means (e.g. slider) of a tool with an axis (follow-up target axis) for driving the conveyer.
In this case, actual processing by the tool is started after the synchronization completes (after the moving speed of the tool by the follow-up axis catches up with and matches with the moving speed of the work by the follow-up target axis), but in many cases the positioning of the tool for preparation to start the processing, such as moving the tool closer to the work in a direction perpendicular to the moving direction of the conveyer (hereinafter referred to as “advanced operation”), is required.
Such a preparation operation does not require the synchronization of axes, and need not be performed in a status where the synchronization of the follow-up axis and the follow-up target axis has completed, but in a conventional process, the preparation operation waits until the tool on the follow-up axis synchronizes with the work on the follow-up target axis (moving at a same speed in a prescribed direction), then (after the synchronization completes), the preparation operation is performed, and the processing is executed using the tool on the follow-up axis.
In other words, conventionally the operations of an object (the tool, in the case of the above example) on the follow-up axis can be separated into an operation not related to synchronization and an operation related to synchronization (processing by the tool, in the case of the above example), and even if “an operation not related to synchronization (advanced operation before processing, in the case of the above example)”, which is supposed to be executed before operations related to synchronization, exists, no information on time required to enter synchronization status (time which elapses from the start to synchronization to the completion of synchronization) is available, so processing for operations not related to synchronization (processing for advanced operation which is not related to synchronization) is executed after completion of synchronization (after synchronization status is established) (see Japanese Patent Application Laid-Open No. 4-223506).
This means that time required for processing for the advanced operation, which is not related to synchronization, and the execution of an operation based on this processing elapses after completion of synchronization and processing for operation, which is related to synchronization and execution of an operation based on this processing delays accordingly. This generates a kind of loss time, and interferes with a decrease in the cycle time in an application which performs synchronous control.